How do I use bike gears properly?

What each shifter does, spinning rather than grinding, changing before the hill, and the cross-chaining to avoid.

Difficulty: beginner
Time: 25 min
Read: 4 min

Short answer

The left shifter makes big changes at the front, the right makes small ones at the back. Aim to keep pedalling at a steady, light cadence of about 70 to 90 turns a minute, change down before the hill rather than on it, and ease off the pedals as you shift.

Most people who find cycling harder than it should be are pushing too big a gear too slowly. Gears exist so that your legs can turn at roughly the same comfortable speed whatever the terrain.

How bike gears combine, and the cross-chaining to avoid

Step by step

Learn what each shifter does.Left hand controls the front chainrings and makes large jumps in effort. Right hand controls the rear cassette and makes small adjustments. Most riding uses the right hand.
Know which way is easier.Small chainring at the front and large sprocket at the back is easiest, for climbing. Large chainring and small sprocket is hardest, for speed. Confusingly, the large ring at the front is hard and the large sprocket at the back is easy.
Aim for a light, steady cadence.Around 70 to 90 pedal revolutions a minute. It feels too easy at first if you are used to grinding, and it is much less tiring and far kinder to your knees.
Change down before the hill.As you approach it, while the pedals are still turning easily. Shifting under heavy load halfway up a climb is where chains skip and derailleurs get damaged.
Keep pedalling as you shift.The chain has to be moving to change. Ease off the pressure — do not stop pedalling entirely — and shift while the cranks are turning.
Never shift while stationary.The chain cannot move to another sprocket, so nothing happens until you set off, when it jumps under load and can throw the chain off.
Shift the front early, then trim with the back.Drop to the small chainring at the bottom of a hill, then use the rear to fine-tune. Trying to make a big front change mid-climb is what drops chains.
Avoid the extreme diagonals.Small ring with the smallest rear sprocket, or big ring with the largest, runs the chain at a sharp angle. It is noisy, inefficient and wears the chain and sprockets quickly.
Anticipate junctions and hills.Change down as you slow for a junction so you are in an easy gear to pull away. Setting off in a high gear is hard work and unstable.
Use the whole range.Most people ride in three or four gears out of eighteen. Deliberately practising the full range on a quiet ride makes it automatic.
Listen to the drivetrain.A quiet chain means a good chain line and a properly indexed gear. Persistent rattling means the gear is not fully engaged or the indexing needs adjusting.

Tips

Spin, do not grind. A light cadence is faster over distance and much easier on the knees.
Change down before the hill, not on it.
If the drivetrain is noisy, you are probably cross-chained or the indexing needs adjusting.

Common mistakes

Pushing a big gear slowly — It loads the knees heavily, fatigues the muscles far faster than spinning does, and is slower over any distance. A lighter gear at a higher cadence is less effort for the same speed.
Shifting hard under full pedal pressure on a climb — The chain is being pulled tight across the sprockets, so it crunches, may skip, and can bend the derailleur or snap the chain. Ease off for half a pedal stroke as you shift.

If it doesn't work

Chain rattles constantly

Cause: Gear not fully engaged, or cross-chained — Fix: Trim the shifter, or move to a less extreme combination; if it persists, the indexing needs adjusting.

Chain drops off the chainring

Cause: Front shift made under load — Fix: Shift the front early and gently, and check the front derailleur limit screws.

Gears skip under pressure

Cause: Worn chain or cassette, or stretched cable — Fix: Check chain wear and replace as a set if needed; a new cable often cures skipping on an older bike.

Cannot reach the lowest gears

Cause: Cable tension or limit screws — Fix: Adjust the barrel adjuster a half turn at a time, or have the gears indexed.

Struggling on every hill

Cause: Not using the small chainring — Fix: Use the left shifter — many people never leave the big ring and make every hill twice as hard.

Questions people ask

What cadence should I aim for?

Around 70 to 90 revolutions a minute for most riders. Count your right leg for fifteen seconds and multiply by four. Most beginners are well below this range.

What is cross-chaining and does it matter?

Running the chain at an extreme diagonal — smallest front with smallest rear, or largest with largest. It is noisy, slightly less efficient and measurably increases wear, so it is worth avoiding as a habit.